Subterranean deposits of coal, also referred to as coal seams, contain substantial quantities of entrained methane gas. Other types of formations, such as shale, similarly contain entrained formation gases. Production and use of these formation gases from coal deposits and other formations has occurred for many years. Substantial obstacles, however, have frustrated more extensive development and use of gas deposits in subterranean formations.
One recently developed technique for producing formation gases is the use of a dual well system including a vertical well bore that is drilled from the surface to the subterranean formation and an articulated well bore that is drilled offset from the vertical well bore at the surface, that intersects the vertical well bore proximate the formation, and that extends substantially horizontally into the formation. This horizontal well bore extending into the formation may then be used to drain formation gases and other fluids from the formation. A drainage pattern may also be formed from the horizontal well bore to enhance drainage. These drained fluids may then be produced up the vertical well bore to the surface.
Although such a dual well system may significantly increase production of formation gases and fluids, some problems may arise in association with the use of such a system. Such problems may include surging of gases being produced and build-up of particles from the formation (such as coal fines), both of which may reduce the efficiency of production from the dual well system. Such problems may also occur with single well systems.